What are wormholes?

Wormholes connecting different points in space and time might seem like the stuff of science fiction, but these mysterious tunnels are an actual feature of theoretical physics. Scientists have yet to find evidence of a wormhole in the cosmos, but the passages are mathematically possible according to Albert Einstein’s theory of general relativity. In the same way that a piece of paper can be folded in half, general relativity states that high mass can bend the fabric of space itself. In 1935, Einstein and physicist Nathan Rosen postulated that this process could result in a bridge forming between two previously separate destinations in space-time. If general relativity holds true, then these “Einstein-Rosen Bridges,” or wormholes, could act as shortcuts to the far off reaches of the cosmos.

Without the luxury of directly observing a wormhole, scientists can only speculate on how they might operate. A common theory suggests that a black hole—a point in space-time where gravity is so strong that even light cannot escape—might serve as the entrance. This opening would connect to a tube, or “throat,” that would empty from a theoretical “white hole,” a point from which light and matter could exit. Still, chances are slim that this kind of wormhole could be used for space travel. The passages are likely to exist only on a tiny subatomic scale, and even if they were large enough to traverse, gravitational forces would cause them to collapse only an instant after they opened. Scientists have theorized that wormholes made of a hypothetical exotic matter might contain enough negative energy to remain stable, but even then the addition of an outside object—like a spaceship—could cause the tunnel to fall apart.

Assuming the power of wormholes could be harnessed, their potential would be extraordinary. By taking a shortcut through a stabilized wormhole, an object could arrive at its destination faster than a beam of light traveling in normal space, opening the door to the possibility of time travel into both the future and the past. Yet another mind-bending theory holds that wormholes could act as portals not just to other points in our universe, but to different universes altogether.